This question already has an answer here:
How to convert 'wchar_t *' to 'const char *'
(1 answer)
Closed 9 years ago.
I am a kind of new for c++ , while working on the windows CE .net compact application
while trying to write hexa datas to a file
CString dataBlock1;
dataBlock1 = "";
CString temp;
for(int i = 0; i < rLen; i++)
{
temp.Format(L"%02X ",rec[i]);
dataBlock1 += temp;
}
std::ofstream out(file);
I am getting this error can not convert parameter 1 from wchar * to const char*
on while using the below write function to write hexa datas to a file
out.write(myReader.dataBlock1.GetBuffer(),myReader.dataBlock1.GetLength());
how can we convert wchar_* to const char* to make the write function work.
Thanks.
You can use the wcstombs function, reference here.
Windows has a set of classes and functions that take wchar_t, which is text stored as UTF-16, and char, which is text stored in your ANSI character set. If you have pointer to wchar_t you either need to use an appropriate class or function that accepts wchar_t, or you need to convert the data to your ANSI character set.
In this case, you want the wchar_t variant of ofstream, wofstream.
Related
This question already has answers here:
C++ Convert string (or char*) to wstring (or wchar_t*)
(19 answers)
Closed 2 years ago.
To convert a string literal to wchar_t we can use L like:
wchar_t variable[10] = L"some text";`
But if the string is stored inside a variable then how do I convert it to wchar_t?
Suppose the string is in a variable
string varString="someText";
I want to store it in a variable of type wchar_t, for example wchar_t var;
How do I type cast and store it?
I want to place the variables inside a loop where their values will change with each cycle:
for(i=0;i<10;i++)
{
var=(*some kind of casting*)varString;
}
Two different ways...depending on simplicity... This is in Visual C++ group...
So first I would try using CStringW. Depending on #defines your regular CString might be a CStringA or CStringW. But, you can say CStringW.
CStringW sWide = "abcdef"; // uses current thread code page
const wchar_t* pWide = sWide.GetString(); // pointer only valid for scope of sWide
Or you can use MultiByteToWideChar() API.
wchar_t wszBuf[512];
MultiByteToWideChar(CP_ACP, 0, "abcdef", 6, wszBuf, _countof(wszBuf)); // substitute "abcdef" and the 6 (length) for your usage...
This question already has answers here:
How to concatenate multiple CString
(2 answers)
Closed 8 years ago.
In my program, I need put a CString variable in a MessageBox. I use the following code:
messagebox("hi" + txt);
But I get the following error message:
error C2678: binary '+' : no operator found which takes a
left-hand operand of type 'const char [3]' (or there is no acceptable
conversion)
you can use a CString variable to format, then pass it to MessageBox.
_T() is a macro for Unicode or MBCS.
you should make sure txt is same encode as str,
CString str ;
str.Format(_T("Hi %s"), txt);
Use format method of the CString. The Format method do thing like how printf, sprintf works.
Example
CString str ;
str.Format("Hi %s", txt);
Use the _T macro to wrap the string literal into a CString:
messagebox(_T("hi") + txt);
Is there any method?
My computer is AMD64.
::std::string str;
BOOL loadU(const wchar_t* lpszPathName, int flag = 0);
When I used:
loadU(&str);
the VS2005 compiler says:
Error 7 error C2664:: cannot convert parameter 1 from 'std::string *__w64 ' to 'const wchar_t *'
How can I do it?
First convert it to std::wstring:
std::wstring widestr = std::wstring(str.begin(), str.end());
Then get the C string:
const wchar_t* widecstr = widestr.c_str();
This only works for ASCII strings, but it will not work if the underlying string is UTF-8 encoded. Using a conversion routine like MultiByteToWideChar() ensures that this scenario is handled properly.
If you have a std::wstring object, you can call c_str() on it to get a wchar_t*:
std::wstring name( L"Steve Nash" );
const wchar_t* szName = name.c_str();
Since you are operating on a narrow string, however, you would first need to widen it. There are various options here; one is to use Windows' built-in MultiByteToWideChar routine. That will give you an LPWSTR, which is equivalent to wchar_t*.
You can use the ATL text conversion macros to convert a narrow (char) string to a wide (wchar_t) one. For example, to convert a std::string:
#include <atlconv.h>
...
std::string str = "Hello, world!";
CA2W pszWide(str.c_str());
loadU(pszWide);
You can also specify a code page, so if your std::string contains UTF-8 chars you can use:
CA2W pszWide(str.c_str(), CP_UTF8);
Very useful but Windows only.
If you are on Linux/Unix have a look at mbstowcs() and wcstombs() defined in GNU C (from ISO C 90).
mbs stand for "Multi Bytes String" and is basically the usual zero terminated C string.
wcs stand for Wide Char String and is an array of wchar_t.
For more background details on wide chars have a look at glibc documentation here.
Need to pass a wchar_t string to a function and first be able to create the string from a literal string concantenated with an integer variable.
The original string looks like this, where 4 is the physical drive number, but I want that to be changeable to match whatever drive number I want to pass to the function
auto TargetDrive = L"\\\\.\\PhysicalDrive4";
The following works
int a = 4;
std::string stddrivestring = "\\\\.\\PhysicalDrive" + to_string(a);
std::wstring widedrivestring = std::wstring(stddrivestring.begin(), stddrivestring.end());
const wchar_t* TargetDrive = widedrivestring.c_str();
This question already has answers here:
C++ convert char to const char*
(5 answers)
Closed 10 years ago.
I need to convert a character in a character array to a const char * in order to print it to a file using fstream. I'm not sure exactly how to do so. I've tried putting the single char into a string, then using c_str(), but that does not work..
If you want to write a single character, just use operator<<:
char arr[256] = "...";
fstream f(...);
f << arr[2];
You don't need to convert the character to a C string.
Hm... If you have a character array, that already decays into char * when passed to a function.
If you need only one character:
char array[128]; // whatever - you want to extract the char from this
char s[] = { array[64], 0 };
then use s which now can decay into char *.
Edit: D'oh, I just read this:
in order to print it to a file using fstream
Well, then don't bother converting it to a proper C string. operator<< knows its job, and it's overloaded for char too.
Is there any method?
My computer is AMD64.
::std::string str;
BOOL loadU(const wchar_t* lpszPathName, int flag = 0);
When I used:
loadU(&str);
the VS2005 compiler says:
Error 7 error C2664:: cannot convert parameter 1 from 'std::string *__w64 ' to 'const wchar_t *'
How can I do it?
First convert it to std::wstring:
std::wstring widestr = std::wstring(str.begin(), str.end());
Then get the C string:
const wchar_t* widecstr = widestr.c_str();
This only works for ASCII strings, but it will not work if the underlying string is UTF-8 encoded. Using a conversion routine like MultiByteToWideChar() ensures that this scenario is handled properly.
If you have a std::wstring object, you can call c_str() on it to get a wchar_t*:
std::wstring name( L"Steve Nash" );
const wchar_t* szName = name.c_str();
Since you are operating on a narrow string, however, you would first need to widen it. There are various options here; one is to use Windows' built-in MultiByteToWideChar routine. That will give you an LPWSTR, which is equivalent to wchar_t*.
You can use the ATL text conversion macros to convert a narrow (char) string to a wide (wchar_t) one. For example, to convert a std::string:
#include <atlconv.h>
...
std::string str = "Hello, world!";
CA2W pszWide(str.c_str());
loadU(pszWide);
You can also specify a code page, so if your std::string contains UTF-8 chars you can use:
CA2W pszWide(str.c_str(), CP_UTF8);
Very useful but Windows only.
If you are on Linux/Unix have a look at mbstowcs() and wcstombs() defined in GNU C (from ISO C 90).
mbs stand for "Multi Bytes String" and is basically the usual zero terminated C string.
wcs stand for Wide Char String and is an array of wchar_t.
For more background details on wide chars have a look at glibc documentation here.
Need to pass a wchar_t string to a function and first be able to create the string from a literal string concantenated with an integer variable.
The original string looks like this, where 4 is the physical drive number, but I want that to be changeable to match whatever drive number I want to pass to the function
auto TargetDrive = L"\\\\.\\PhysicalDrive4";
The following works
int a = 4;
std::string stddrivestring = "\\\\.\\PhysicalDrive" + to_string(a);
std::wstring widedrivestring = std::wstring(stddrivestring.begin(), stddrivestring.end());
const wchar_t* TargetDrive = widedrivestring.c_str();